Composite materials are widely used to create structures that are light in weight, have great strength, and can resist high temperatures. The basic structural member is a filament or yarn which includes both a reinforcement fiber such as graphite, and another fiber that provides a matrix for supporting and positioning the reinforcement fiber.
In past years a thermoset epoxy resin has been commonly used as the matrix fiber of the filament. The thermoset material becomes chemically and permanently cross-linked when exposed to heat, hence cold storage may be required prior to its use in manufacturing a part. Recent advancements in the technology, however, have made it possible to use a thermoplastic material instead of the thermoset. Thermoplastics merely undergo a reversible phase change, from solid to liquid, when exposed to elevated temperatures, and once cooled, the thermoplastic matrix returns to its original solid phase. Some significant advantages of the thermoplastic matrix are described in an article entitled "Thermoplastic/Graphite Fiber Hybrid Fabrics" published by the Society for the Advancement of Material and Process Engineering in the SAMPE Journal, Vol. 25, No. 1, January/February 1989. Thus, the thermoplastic composite (or TPC) filament is now widely used in the industry.
A structure or part is typically created by a preliminary formation, and by then heating it in an oven to form the final part which when cooled has the rigidity of titanium or steel. That procedure can become very cumbersome and expensive, however, particularly where articles of large size are being formed.
The present invention relates to a method and apparatus for forming structures or parts from composite material, without the use of an oven, and in particular, relates to forming them from thermoplastic composite (or TCP) filament.